The manufacture of magnetic read/write heads for magnetic media data storage devices requires that the head be processed through a number of successive operations. For example, the heads may be produced as a wafer, divided first into bars and then into individual head elements with the head elements being formed into "slider" assemblies. The slider is then mounted, with corresponding suspension appendages and bonding wires, on a Head Gimble Assembly ("HGA"). The HGA includes a suspension for enabling the read and write elements to fly over a disk drive surface. The HGA is installed into the disk drive, where the head is tested in conjunction with other components of the disk drive. Each of these procedural steps adds additional manufacturing costs.
Due to the extremely tight tolerances which such heads must achieve for use with today's high density hard disk media, end of process testing of the head assemblies reveals a significant number of defective or unacceptable devices. Therefore, it would be desirable to be able to test the heads during the manufacturing process such that, at each such process step, those heads which were defective could be discarded and no expense would be incurred in further processing such defective heads. It is also significant that the head elements may become damaged during any of the previously discussed manufacturing operations, and so it might also be desirable to test the head elements at more than one stage in the overall manufacturing process. Of course, since there is cost involved in the testing process itself, in order to be cost effective, any such test must be easily and quickly performed and further must not, itself, be a significant cause of damage to the head elements.
The above problems being recognized in the industry. There have been several attempts to provide testing facilities for less than totally assembled head elements. For example, a head tester is disclosed in U.S. Pat. No. 3,699,430, issued to Kruklitis. The Kruklitis invention utilizes a rotating drum with a strip of magnetic recording material thereon. However, although the Kruklitis invention is well suited for some head devices, due to the close proximity to the media required by hard disk heads and the high speed at which the media is moved in hard disk assemblies, this invention will not effectively duplicate the conditions under which a fixed disk head element will be required to operate.
To the inventor's knowledge, prior successful attempts at producing a testing means for less than fully assembled fixed disk heads have all involved subjecting the element to be tested to a variable magnetic field produced by a stationary field source. An example of such a "static" head testing device is found in U.S. Pat. No. 3,706,926, issued to Barrager et al., which patent discloses a method for testing batch fabricated heads. The device of that patent applies a test magnetic field to the head under test by way of an adjacent conductive strip, or an adjacent inductive magnetic head driven by a current. Such tests have achieved the objective of being relatively easy and relatively harmless to the element under test. However, such tests are also clearly less than optimal in that such a "static" test may not accurately predict the characteristics of the head element as the head is required to write to and/or to read from moving magnetic media, as will be required of the finished head assembly.
It has been understood in the field that static testing, as described previously herein, is less accurate than is "dynamic" testing, wherein a head is tested actually reading and/or writing to moving media. Nevertheless, the static test has been thought to be an optimal compromise since, prior to the present invention, it has been thought that dynamic testing of an unmounted head element would be too difficult or too costly given that the necessarily close proximity of the head to a rapidly rotating disk medium would require slow and careful positioning of each head (a time consuming and, therefore, costly proposition), and further would be likely to frequently damage heads and/or the expensive hard disk medium.
To the inventor's knowledge, either the idea of using a floppy disk to test a hard disk head had not previously occurred, or else it had been summarily dismissed, given that those skilled in the art will readily recognize that a floppy disk could not, prior to the present invention, achieve the necessary stability in the necessarily close proximity to a head under test at the required rotational speed (even using the known stabilizer plate which is currently used in the industry in some applications as a stabilizer for rotating floppy disks at higher the usual rotational speeds). This is particularly true since the apparatus for holding the hard disk heads (or head bars, or the like) would be necessarily quite massive compared to a simple floppy disk head assembly, and thus would tend to interfere with the stability of the floppy disk when brought into close proximity. Indeed, the hard disk heads, or head bar assemblies, or the like would themselves become a cause of instability of the floppy disk when brought into close proximity thereto.
To the inventor's knowledge, no cost effective prior art means for dynamically testing fixed disk head elements prior to final assembly has been produced. All such test means have either been of the static type or else have been unsuitable or cost ineffective for use with fixed disk head elements.